In ophthalmic surgery, and in particular in vitreo-retinal surgery, it is desirable to use a wide-angle surgical microscope system to view as large a portion of the retina as possible. Wide-angle objective lenses for such microscopic systems exist, but they require a wider illumination field than that provided by the cone of illumination of a typical fiber-optic probe. As a result, various technologies have been developed to increase the beam spreading of the relatively incoherent light provided by a fiber-optic illuminator. These known wide-angle illuminators can thus illuminate a larger portion of the retina as required by current wide-angle surgical microscope systems and/or surgeon requirements. Currently existing wide-angle illuminators, however, display several disadvantages.
One disadvantage of prior art wide-angle illuminators for ophthalmic surgery is the high precision required in the fabrication of the surfaces of the lenses used in the distal end of the illuminators. These lenses (optical elements) are typically optically coupled to, for example, an optical fiber carrying light from an illumination source, and act to scatter or otherwise diverge the incoming light to illuminate a surgical field. The high precision required to produce these conventional optical elements makes miniaturization (required for surgical endoilluminators) more difficult and raises the cost of production.
Another disadvantage of currently available wide-angle illuminators is glare. Glare results when the source of the illumination is small and bright, and the user (e.g., an ophthalmic surgeon) has a direct line of sight to the small bright illumination source. Glare is unwanted stray radiation that provides no useful illumination, and either distracts an observer or obscures an object under observation. Current wide-angle illuminators typically use non-flat lenses that extend beyond the distal end of the cannula to deliver light to a surgical site. These non-flat, extending optical elements are used to provide increased (wide-angle) light dispersion, but have the disadvantage of being a bright point source of glare for the surgeon. Glare can be corrected for in current wide-angle illuminators, but typically only by reducing the total illumination light flux, which reduces the amount of light available for observation by the surgeon. For example, the “bullet probe” manufactured by Alcon Laboratories, Inc., of Fort Worth, Tex., achieves wide-angle illumination by using a bullet-shaped fiber having a surface diffusive finish to scatter light emanating from the distal end of an optical fiber. To reduce glare, the bullet probe can use a geometric shield, which reduces the illumination angle by reducing the overall available light flux.
A further disadvantage of some prior art wide-angle illuminators is that the rounded or pointed surface of their distal end optical elements provide a larger and more adherent surface for blood while in a surgical environment. Blood covering the optical element at the illuminator tip can result in thermal damage to the optical element and to the optical fiber carrying light from a high intensity light source due to increased heating of the optical element caused by the blood blocking light transmission.
Therefore, a need exists for a surgical wide-angle illuminator that can reduce or eliminate these and other problems associated with prior art wide-angle illuminators.